Thermo-electric Thermometer.
A species of differential thermometer. It consists of two
thermo-electric junctions connected in opposition with a galvanometer in
the circuit. Any inequality of temperature in the two ends or junctions
produces a current shown by the galvanometer. It may be used to
determine the temperature of a distant place, one of the junctions being
located there and the other being under control of the operator. If the
latter junction is heated until no current is produced its temperature
is evidently equal to that of the distant couple or junction. The
heating may be done with hot water or mercury, or other melted metal.
The temperature of the water, or other substance, gives the temperature
of the distant place.
Thermolysis.
Decomposition by heat; dissociation. All compound bodies are
decomposable by heat if it is intense enough. Hence at very elevated
temperatures there can be no combustion.
Synonym--Dissociation.
Thermometer.
An instrument for indicating the intensity of heat. Three scales of
degrees of heat are used in practise, the Fahrenheit, Réamur, and
Centigrade, each of which is described under its own title. (See Zero,
Thermometric-Zero, Absolute.) The ordinary thermometer depends on the
expansion of mercury; in some cases alcohol is used. Besides these the
compound bar principle as used in the thermostat (see Thermostat,
Electric) is employed.
Thermometer, Electric.
(a) A thermometer whose indications are due to the change of resistance
in conductors with change of temperature. Two exactly similar resistance
coils maybe electrically balanced against each other. On exposing one to
a source of heat, its resistance will change and it will disturb the
balance. The balance is restored by heating the other coil in a vessel
of water when the temperature of the water gives the temperature of both
coils. The coils are enclosed in water-tight metallic cases.
Synonym--Electric Resistance Thermometer.
(b) A differential thermometer may be made by connecting with a pair of
conductors, two thermo-electric couples in opposition to each other, and
including a galvanometer in series. On heating the junction of one
couple more than that of the other a current at once goes through the
galvanometer.
(c) (See Thermometer, Kinnersley's.)
Synonym--Thermo-electrometer.